Various types of seat heaters have been used in automobiles to heat occupied seats and improve passenger comfort. A vehicle seat heater is required to be strong and durable to accommodate bending without stretching to maintain integrity of the conductor traces comprising the heater. It is known to provide a self-regulating heater on a flexible substrate that can withstand flexing and temperature variations and resist moisture. Exemplary automobile seat heaters can be found, for example, in U.S. Pat. Nos. 6,884,965 and 7,202,444. The seat heaters disclosed therein can be made by polymer thick film printing processes, which are known to those skilled in the art.
Occupant sensors have been incorporated into automobile passenger compartments for determining when a seat is occupied and alerting passengers if seatbelts are not fastened for all occupants. In more sophisticated occupant sensor systems, vehicle air bags can be activated or deactivated based on sensed occupancy. Deployment characteristics of an airbag system may be controlled and changed based on the sensed mass of the occupant, to operate differently for children or smaller adults than for larger occupants. Different types of sensor systems have been used. Some occupant sensor systems discriminate only on differences in mass and do not distinguish between, for example, a small child and an object of similar mass placed on the seat. A more sophisticated occupant sensor technology, referred to herein as a capacitor system, utilizes electric field imaging technology to determine occupancy and distinguish between human occupants and other articles or things that may be placed on a vehicle seat. A flexible antenna is placed in the automobile seat and operates as one plate spaced from a second plate defined by the roof of the vehicle, the windshield or other structure to establish charge separation in a parallel plate capacitor creating an internal electric field. A polarized dielectric interposed between the spaced plates reduces the electric field and increases the capacitance. By sensing capacitance changes that occur when a person or thing is positioned between the plates, and comparing to the known capacitance of air between the antenna and plate, software can discriminate between persons and things, and can evaluate the size of a person occupying the seat. A controller can then use the information obtained from the sensor to provide operating signals for controlling various systems that interact with the occupants.
It is known to provide seat heaters and occupant sensors as separate individual systems. Installation of the separate individual components of each system can be both difficult and time consuming. It is also known to provide intra-seat structures that combine components for seat heater and occupant sensing systems of some types, such as that shown in U.S. Pat. No. 7,500,536 which utilizes a self-regulating heater and a mass sensor. However, it has not been known to combine the more sophisticated capacitor system occupant sensors with seat heaters due to interference generated in the performance of capacitor system sensor by operation of the seat heater. Even providing these systems as separate individual components in a seat has been difficult, due to the interference problem.
It would be advantageous to combine in a single seat structure both a self-regulating heater component and an antenna for an occupant sensor capacitor system.